How to see output of cmake's add_custom_command - cmake

Question

The add_custom_command is lisently failing if run from CMakeLists.txt
Is there a way to see in console what's happening when the command is executed?
EDIT: The code:
I tried to run examples from the repository but they didn't work.
The code is modified a little because I was trying to make it work somehow. If the command is run from the terminal it works, but cmake just refuses to work. And there is no output saying why it fails.
cmake_minimum_required(VERSION 3.5)
project(test LANGUAGES CXX)
set(CMAKE_INCLUDE_CURRENT_DIR ON)
set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
find_package(Qt5Core)
find_package(Qt5Gui)
find_package(Qt5Widgets)
# Download automatically, you can also just copy the conan.cmake file
if(NOT EXISTS "${CMAKE_BINARY_DIR}/conan.cmake")
message(STATUS "Downloading conan.cmake from https://github.com/conan-io/cmake-conan")
file(DOWNLOAD "https://raw.githubusercontent.com/conan-io/cmake-conan/master/conan.cmake"
"${CMAKE_BINARY_DIR}/conan.cmake")
endif()
include(${CMAKE_BINARY_DIR}/conan.cmake)
conan_cmake_run(CONANFILE conanfile.txt
BASIC_SETUP)
get_filename_component(hw_proto "protos/test.proto" ABSOLUTE)
get_filename_component(hw_proto_path "${hw_proto}" PATH)
# Generated sources
set(hw_proto_srcs "${CMAKE_CURRENT_BINARY_DIR}/test.pb.cc")
set(hw_proto_hdrs "${CMAKE_CURRENT_BINARY_DIR}/test.pb.h")
set(hw_grpc_srcs "${CMAKE_CURRENT_BINARY_DIR}/test.grpc.pb.cc")
set(hw_grpc_hdrs "${CMAKE_CURRENT_BINARY_DIR}/test.grpc.pb.h")
message("CHECKING GRPC.
PROTOC: ${CONAN_BIN_DIRS_PROTOBUF}/protoc
AND PLUGIN: ${CONAN_BIN_DIRS_GRPC}/grpc_cpp_plugin
and lib dir ${CMAKE_CURRENT_BINARY_DIR} from ${hw_proto}
${hw_proto_srcs}
${hw_proto_hdrs}
${hw_grpc_srcs}
${hw_grpc_hdrs}
${hw_proto}
${hw_proto_path}
")
add_custom_command(
OUTPUT "${hw_proto_srcs}" "${hw_proto_hdrs}" "${hw_grpc_srcs}" "${hw_grpc_hdrs}"
COMMAND ${CONAN_BIN_DIRS_PROTOBUF}/protoc
ARGS --grpc_out="${CMAKE_CURRENT_BINARY_DIR}"
--cpp_out="${CMAKE_CURRENT_BINARY_DIR}"
--proto_path="${hw_proto_path}"
--plugin=protoc-gen-grpc="${CONAN_BIN_DIRS_GRPC}/grpc_cpp_plugin"
test.proto
)
add_executable(test
main.cpp
)
target_link_libraries(test Qt5::Core Qt5::Widgets Qt5::Gui pthread)
target_include_directories(test PRIVATE ${CMAKE_CURRENT_BINARY_DIR})

Answer 1

One way to see all commands being executed is to call cmake with the --verbose option.